Question: Kevin is $39$ years old and Daniel is $3$ years old. How many years will it take until Kevin is only $4$ times as old as Daniel?
Explanation: We can use the given information to write down an equation about how many years it will take. Let $y$ be the number of years that it will take. In $y$ years, Kevin will be $39 + y$ years old and Daniel will be $3 + y$ years old. At that time, Kevin will be 4 times as old as Daniel. Writing this information as an equation, we get: $39 + y = 4 (3 + y)$ Simplifying the right side of this equation, we get: $39 + y = 12 + 4 y$. Solving for $y$, we get: $3 y = 27$. $y = 9$.